This invention relates to wear and temperature resistant polycrystalline diamond bodies for use as tools in cutting, machining and drilling operations and as wear surfaces.
On the market there already exists a number of different high pressure-high temperature sintered tools containing polycrystalline diamond as the main ingredient. These tools are produced in different countries like USA, Japan, Ireland, Sweden, France, USSR, South Africa, etc. and are used for different purposes, among which the most important ones are rotating rock drilling (oil drilling), metal cutting and wire drawing.
The technique when producing such polycrystalline diamond tools using high pressure-high temperature (HP/HT) has been described in a number of old patents, e.g.:
U.S. Pat. No. 2,941,248: "High temperature high pressure apparatus"
U.S. Pat. No. 3,141,746: "Diamond compact abrasive": High pressure bonded body having more than 50 vol % diamond and a metal binder: Co, Ni, Ti, Cr, Mn, Ta etc. causing "interlocking of diamond-to-diamond interfaces". Without any supporting body.
U.S. Pat. No. 3,239,321: "Diamond abrasive particles in a metal matrix": High pressure sintering of diamond together with different metals. Without any supporting body.
U.S. Pat. No. 3,407,445: Process and apparatus for the production of polycrystalline diamond bodies. Without any supporting body.
All these patents disclose the use of a pressure and a temperature during the sintering where diamond is the stable phase. Tools are described having more than 50 vol % diamond and a binder metal, e.g. Co or Ni, but without any supporting body.
In some later patents: e.g. U.S. Pat. Nos. 3,745,623 and 3,767,371 high pressure-high temperature sintered polycrystalline diamond tools are described where the superhard body, containing more than 70 vol % diamond, is bonded to a disk of cemented carbide: "said diamond crystalline material and said cemented carbide being joined at an interface, said interface consisting solely of cemented carbide and diamond crystals".
The patent U.S. Pat. No. 4,311,490 describes a high pressure-high temperature sintered body comprising at least two layers of diamond (or cBN) on top of each other and bonded to a disk of cemented carbide. The diamond grain size of the top layer is below 10 .mu.m and of the bottom layer below 70-500 .mu.m. In this case, too, the condition is that the amount of diamond (cBN) is more than 70 vol % and that the diamond (cBN) grains in the bottom layer lie in direct contact with the sintered carbide of the supporting disk. Still another condition is that the diamond (cBN) grains are directly bonded to each other and that the hard layers, apart from diamond (cBN), only contain metals.
The patent U.S. Pat. No. 4,403,015 describes the use of nonmetallic intermediate layers consisting of cubic boron nitride (below 70 vol %) and one or more carbides, nitrides, carbonitrides or borides between the superhard polycrystalline diamond layer and the support disk.
A number of other patents describe the use of metallic intermediate layers between the diamond (cBN) layer and the supporting disk. e.g.:
U.S. Pat. No. 4,063,909: "Abrasive compact brazed to a backing": an intermediate layer, &lt;0.5 mm thick, of Ti, Cr, Mn, V, Mo, Pt, Fe, Co, Ni, etc. HP/HT sintered.
U.S. Pat. No. 4,108,614: "Zirconium layer for bonding diamond compact to cemented carbide backing". HP/HT sintered.
U.S. Pat. No. 4,228,942: "Method of producing abrasive compacts": Ti and Ag-Cu-Zn-Ni-Mn brazed at 750.degree. C.
U.S. Pat. No. 4,229,186: "Abrasive bodies": A laminated abrasive body which is in effect a thick compact comprising a plurality of diamond compacts laminated together, joining of adjacent compacts taking place by means of a layer of metal, e.g. 100 .mu.m Zr, or a metal alloy braze and the thickness of the laminate exceeding 5 mm. Each diamond body consists of 80 vol % diamond and 20 vol % of metal, e.g. Co.
U.S. Pat. No. 4,293,618: "Sintered body for use in a cutting tool and the method for producing the same". The supporting disk is here (Mo,W)C+Co. In some of the examples an intermediate layer of a metal, e.g. Mo, W, Nb, Ta, Ti, Zr or Hf is used between the supporting disk and the hard body of diamond or cubic boron nitride.
U.S. Pat. No. 4,411,672: "Method for producing composite of diamond and cemented tungsten carbide". Between the diamond powder and the supporting disk of (WC+Co) an intermediate layer of a metal, e.g. Co--Ni--Fe--alloy, having a metal point lower than the eutectic point of the WC--Co--composition is used. The sintering is made at a temperature where the Co--Ni--Fe--alloy melts but not the (WC+Co) disk.
The patent U.S. Pat. No. 4,604,106: "Composite polycrystalline diamond compact" describes the use of small presintered pieces of cemented carbide as an addition of the diamond grains giving a higher diamond concentration towards the working surface and a lower concentration towards the supporting disk.
In most practical cases the working surface of the polycrystalline diamond body, coming into contact with the work piece, ought to have the highest possible wear resistance and thermal stability. the other side of the diamond body, however, ought to be less rigid or brittle in order to be able to withstand the forces of the clamping without cracking. This is valid for all types of clamping, but the crack tendency is higher in the case where the diamond body is HP--HT--bonded directly to a support of e.g. cemented carbide and the difference in thermal expansion and mechanical properties is great and sharp between the diamond body and the support material.
In order to improve the temperature resistance of polycrystalline diamond tools two different ways have been attempted. Both ways aim at decreasing the thermal expansion of the diamond layer. One method is, according to the patents U.S. Pat. Nos. 3,233,988 and 3,136,615, to use relatively great amounts of binder metals e.g. Co, during the sintering and afterwards leach out the metals by using strong acids, giving a porous and mechanically weaker material. The other method is to put in materials with low thermal expansion like Si, Si--alloys and SiC into the diamond body according to the patents U.S. Pat. Nos. 4,151,686, 4,241,135, 4,167,399 and 4,124,401.
Neither of these known methods, however, solve the problem of giving optimum properties to both the working surface of the polycrystalline diamond tool and the opposite part of the diamond body close to the support material like a disk of cemented carbide or a braze metal or another type of clamping.